I trackedentity an entity, I take some time to track, so I want to add a loading

1. A concise explanation of the problem you're experiencing.

I trackedentity an entity, I take some time to track, so I want to add a loading,how to know loading success

2. A minimal code example. If you've found a bug, this helps us reproduce and repair it.

3. Context. Why do you need to do this? We might know a better way to accomplish your goal.

4. The Cesium version you're using, your operating system and browser.

Are you tracking it using:

viewer.trackedEntity = entity

``

If so, that should be instant, so there shouldn’t be any loading necessary. If you can post a Sandcastle (https://cesiumjs.org/Cesium/Build/Apps/Sandcastle) example of the delay you’re seeing that’d help.

thanks!
actually I use
viewer.trackedEntity = entity .
I think I take some time to track because loading model, how to know loadding entity success.

Unfortunately, this isn’t something that CesiumJS supports. The ready promise is intentionally hidden in the Entity API. You can see the discussion on that here:

You could use the primitive API as described in that issue, but then you won’t be able to use trackedEntity.

If the model takes a significant time to load, this might be a good reason to tile it up into 3D Tiles (which you can do with Cesium ion https://cesium.com/ion/)

thanks,I try it